1. Field of the Invention
The present invention relates to a method of producing an adhesive tape with which electronic parts at the environs of a lead frame, such as leads, diepads and radiant plates, semiconductor chips, are bonded to each other.
2. Description of the Prior Art
Conventional adhesive tapes used for resin package semiconductor devices may be exemplified by lead frame-fixing adhesive tapes, adhesive tapes for radiant plates, and TAB carrier tapes. As for a lead frame-fixing adhesive tape, it is used to fix a lead of a lead frame, with the aim of enhancing the production yield and productivity for the lead frame itself as well as in the whole semiconductor assembly process. Generally, the adhesive tapes are applied on lead frames by lead frame makers and these are used to mount semiconductor chips which are then packaged in a resin by semiconductor assemblers. In connection with these works, the adhesive tapes for fixing lead frames are required to be superior in the reliability, the workability upon taping and the adhesiveness after work as well as to show thermal resistance sufficient to overcome the heating in the assembly process of semiconductor devices.
Examples of the conventional adhesive tapes for these purposes include those in which polyacrylonitrile, polyacrylate or an acrylonitrile-butadiene copolymer alone or in combination with thermosetting resins is coated on thermal resistant support films, such as polyimide films. Recently, the package structures of semiconductor devices have become complex owing to the requirement for multi-pin structure and heat radiation in the semiconductor devices and the organic materials used in the adhesive tapes have been strictly required to be good in electrical, physical and thermal properties and in handling. Conventional adhesive tapes are, however, insufficient in thermal properties, dimensional stability and electrical properties. Particularly, when lead pins are bonded to heat sinks or connected to semiconductor chips through conventional insulating tapes, there is a serious problem in that the metallic materials, such as lead frames, might be bent or damaged.
To solve the problems, U.S. Pat. Nos. 5,494,757 and 5,500,294 disclose liquid adhesives comprising a piperazinylethylaminocarbonyl-containing butadiene-acrylonitrile copolymer and a compound having at least two maleimide groups optionally in combination with a diamine-containing polysiloxane compound. These liquid adhesives can be adhered and cured at a relatively low temperature and have sufficient heat resistance and electrical properties, but have a significant problem of generating a large quantity of out gas.